TFT LCDs have become the most popular flat displays since they have advantages of compactness, low heat generation, long life and visual comfort. In general a TFT LCD includes a backlight module, a first polarizer, a TFT array substrate, a liquid crystal layer, a color filter and a second polarizer. The TFT array substrate forms a plurality of pixels thereon. The liquid crystal layer contains a plurality liquid crystals therein. Originally, each pixel includes three sub-pixels, i.e., a red sub-pixel, a green sub-pixel, and a blue sub-pixel. For such a RGB TFT LCD, the backlight module needs consuming more power in order to have sufficient light passing through the color filter.
To overcome the disadvantage of the RGB TFT LCD, a RGBW TFT LCD is developed, in which each pixel includes a red sub-pixel, a green sub-pixel, a blue sub-pixel, and a white sub-pixel. A transparent area corresponding to the white sub-pixel is defined in the color filter, whereby a light transmittance of the color filter is improved, and the power consumption required by the backlight module can be reduced.
However, for the RGBW TFT LCD, it confronts a problem of horizontal crosstalk which does not occur in the RGB TFT LCD. When the RGBW TFT LCD shows a one-colored segment (for example, an entirely red segment), every pixel in the segment has the same polarity, whereby Vcom couples cannot offset from each other, whereby a horizontal crosstalk happens which results in an uneven grey level beside the red segment. Here Vcom couple means a couple between data lines and an upper common electrode, i.e., CF (color filter) layer Vcom, for providing a bias across the liquid crystals in the liquid crystal layer.